Investors initially didn't seem concerned that until last year, the company was in the red almost every year since its 2003 inception. (In 2006, it turned a slight profit on sales of $32 million.) But shares began dropping in May, and by June 20 LinkedIn was below $64 a share.

A July spike took shares back to nearly $110, but they took another dive in late November when LinkedIn insiders began unloading shares. IPOs typically come with "lockup" agreements preventing employees and early investors from unloading their stakes; LinkedIn's expired on November 20. A few days earlier, LinkedIn revealed that its early investor Bain Capital planned to dump its entire $275 million stake.

An analyst report from Trefis.com called that decline "an implicit acknowledgement that perhaps LinkedIn really is over-valued." Trefis's analysis set a LinkedIn price target of $43 a share -- sharply below the current price.